Rolls-Royce and Gulfstream Aerospace Corp. conducted the first original equipment manufacturer test flight of an ultralong-range business jet powered by 100% Sustainable Aviation Fuel (SAF). The test took place on the BR725-powered Gulfstream G650 twin-jet over Gulfstream’s headquarters in Savannah, Georgia.

Demonstrating that current Rolls-Royce engines for business jet and large civil applications can operate with 100% SAF as a full “drop-in” option, this test lays the groundwork for moving this type of fuel towards certification.

SAF is typically a blend of a renewable synthetic paraffinic kerosene (SPK) fuel—such as HEFA—and petroleum-based Jet A fuel. Current regulations limit the SPK that can be used in jet fuel to a maximum of 50%, as the SPK products lack compounds called aromatics that are necessary to meet current fuel specifications, and also do not have the density required to meet jet fuel specs.

The SAF that was used in the test consists of two components: HEFA (Hydroprocessed Esters and Fatty Acids), produced from waste fat and waste plant oils by low-carbon fuel specialist World Energy in Paramount, California; and SAK (Synthesized Aromatic Kerosene) made from waste plant-based sugars by Wisconsin-based Virent Inc.

Virent’s SAK—derived from plant sugars—provides the necessary aromatics and density to the SPK fuel, eliminating the need for petroleum products and enabling production of a 100% drop-in SAF that can be used in existing jet engines and infrastructure with no modifications.

Virent has also done engine testing that shows a SAK blend has lower particulate matter (PM) emissions than conventional jet fuels because it has different aromatic compounds.

Advantages of a 100% drop-in SAF. Source: Virent.

This sustainable HEFA/SAK blend has the potential to reduce net CO₂ lifecycle emissions by about 80% compared to conventional jet fuel, with the possibility of further reductions in future.

The BR725-powered G650 aircraft family holds more than 120 world speed records, including the speed record for the farthest flight in business aviation history. More than 500 of the aircraft are in service.

The BR725 combines proven features from the BR 700 and Trent families. Compared with its highly successful predecessor, the BR710, the BR725 is more powerful, with a maximum thrust of 16,900lb; is more than 4 dB cumulative quieter; has 4% better specific fuel consumption; and shows 21% improvement in NO_x emissions.